Oshita's business career began with a lemonade stand that he stole from his neighbor. He soon became the biggest lemonade distributor, and then started working for Gozaburo Kaiba at Kaiba Corp. With the other four members of the Big Five, Oshita conspired with Kaiba to take over Kaiba Corp and overthrow Gozaburo. Their plan succeeded, but Kaiba betrayed them, so when Maximillion Pegasus attempted to take over Kaiba Corp, the Big Five joined forces with him to help him. After Pegasus was defeated by Yugi in a duel, Kaiba fired the Big Five, but they trapped him in his own virtual world and attempted to sacrifice him to the lava pit to awaken the Five God Dragon. When Yugi Muto, Katsuya Jonouchi, Mai Kujaku, and Mokuba Kaiba entered the game, the Big Five summoned the Mythic Dragon themselves, but when Yugi and Kaiba combined their monsters to destroy it, the Big Five were imprisoned in the virtual world.
They were there so long their bodies were destroyed, until they found Noah Kaiba and entered his virtual world. They agreed to defeat Yugi, Seto Kaiba, and the others, as they needed to steal their bodies to escape.
Oshita took the form of Deep Sea Warrior and dueled Yugi. His deck is water themed, and he was able to sacrifice two monsters to create a barrier to reflect any of Yugi's attacks back at him. However, with Kuriboh as his deck master (though Yugi intended to choose the Black Magician), he was able to attack Oshita directly and defeat him.Oshita was digitized, but not destroyed; he later returned alongside his defeated comrades Shuzo Otaki, Chikuzen Ooka, and Kogoro Daimon, attempting to steal the bodies of Jonouchi, Shizuka Kawai, and Ryuji Otogi. However, Noah recalled them, as they had not won them in a duel. Eventually they all entered Tristan's body, which had been stolen by Soichiro Ota. They dueled together against Yugi and Jonouchi, rotating around. Oshita was only dueling for one turn before Otaki took over. Yugi and Jonouchi defeated the Big Five. They attempted to steal the gang's bodies again, but Noah sent them back to his room. They asked him for another chance, but he gave them no more chances, and imprisoned them each in a different corner of the virtual world.
Oshita was killed along with Noah, Gozaburo, and the other members of the Big Five when Noah caused a satellite attack that destroyed the fortress that the virtual world was stationed in, deleting the virtual world and anyone in it.
Yu-Gi-Oh! The Abridged Series
In LittleKuriboh's parody Yu-Gi-Oh! The Abridged Series, Gansley's role is mostly similar to his role in the anime, except that he (and the others in the Big Five) are part of 4Kids out to cancel the Abridged Series due to the word "Disney" being mentioned. He was defeated by Yugi, but returned to chase after Joey, Serenity, Tristan, and Duke. After all the Big Five were defeated by Yugi and Joey, Noah punished them by banishing them to the darkest corners of the Internet. Gansley was sent to Megaupload, which was empty.